Hepatitis B virus has been implicated to be the most probable etiologic agent for serum hepatitis or hepatitis of the long incubation variety. At least two distinct antigenic components have been found to be associated with hepatitis B virus. The first one, commonly known as hepatitis B surface antigen (HB.sub.s Ag) is present on the 20-nm spherical or filamentous form and 42-nm Dane particles. The other antigen designated as hepatitis B core antigen (HB.sub.c Ag) is found in the core of the 42-nm Dane particle. The antibodies for the two antigens are designated as anti-HB.sub.s and anti-HB.sub.c respectively. Blood or blood products containing hepatitis B virus can transmit Type B hepatitis following transfusion or parenteral inoculation. HB.sub.s Ag circulates in the blood of patients actuely or chronically infected with hepatitis B virus. Since the original studies on the detection of HB.sub.s Ag by immunodiffusion, several other methods have been developed for identification of this antigen. At present, radioimmunoassay for HB.sub.s Ag appears to offer superior sensitivity than immunodiffusion, complement fixation, counterelectrophoresis and rheophoresis techniques. However, sensitivity of either of these methods for detection of hepatitis B surface antigen has been found to be a major problem in the elimination of post-transfusion, Type B hepatitis.
The radioimmunoassay technique(s) for hepatitis B surface antigen available at the time of invention wherein either the inside of a test tube is coated with anti-HB.sub.s derived from guinea pigs or beads or beadlets consisting of polystyrene or polythylene polymers are coated with anti-HB.sub.s derived from either guinea pigs or human patients. A serum or plasma sample containing hepatitis B antigen when added to the tube, an antigen-antibody complex is formed. When such complex is contacted with the radioactively labeled anti-HB.sub.s, an additional complex is formed comprising of radioactive anti-HB.sub.s ; -HB.sub.s Ag;-non-radioactive anti-HB.sub.s. Any non-complexed radioactive antibody is removed by subsequent washing of the tubes or beads or beadlets. The extent of radiation emitted by such complex is determined and compared with the known control and thereby the presence or absence of hepatitis B antigen is determined.
The object of present invention is to modify the entire methodology including the processes involved so as to achieve better sensitivity and specificity for Hepatitis B antigen (both HB.sub.s Ag and HB.sub.c Ag), which would become more apparent in the following paragraphs.